Photovoltaic (PV) cells are the most efficient devices when absorbing photons with energies similar to its bandgap energy. They are therefore incapable of harvesting sub-bandgap photons in the infrared regime and experience significant thermalization losses when absorbing photons in the visible regime with energies above that of the bandgap energy. This excess heat from both regimes has a detrimental effect on the PV cell’s efficiency and lifetime due to the temperature rise. This dilemma has highlighted the need for a photovoltaic device able to utilize the excess heat generated effectively. In this work, an integrated hybrid photo-thermo-voltaic system is presented. The system is comprised of a plasmonic enhanced silicon PV cell with a nanostructure surface to increase the absorption of the visible spectrum. The cell is attached to a heavily doped silicon-based plasmonic infrared super absorber to trap the thermal/infrared portion of the spectrum, facilitating the harvesting of sub-bandgap photons and excess heat from the thermalization losses. The PV and absorber layers of the solar system can be easily fabricated with low cost due to their CMOS compatibility. This harvested heat energy is then utilized to heat the hot side of a connected thermo-electric generator (TEG), which directly convert waste energy into electric power by creating a temperature gradient across the TEG. This TEGs based on traditional semiconductor material 𝐵𝐵𝑖𝑖2𝑇𝑇𝑒𝑒3. Radiation energy near the bandgap is directly transformed to electricity by PV panel and simultaneously, infrared energy is utilized by the TEG to convert heat to electricity. Consequently, more electricity can be produced by the hybrid system than the power produced by a single PV or TE system. The system exhibits a considerable improvement in efficiency and power output when compared to a standalone PV cell or TEG owing to the utilization of the lost heat and IR solar spectrum. Promising applications of the system include energy storage and solar heating.

The thermoelectric effect can be defined as the power that can be ascribed to the results of the temperature gradient
across a junction between two different metals. Micro thermoelectric generators (μTEGs) are used with energies or
losses that have a gradient in temperature or spatial dimensions that are too small for conventional thermodynamic
heat engines to effectively utilize, delivering micro-Watts to milli-Watts of power per device. Silicon nanowires
(SiNW) thermoelectrical properties are more enhanced compared to thin-layer silicon, mainly due to the decrease of
thermal conductivity caused by the quantum confinement and phonon scattering effects in low dimensions. SiNWs as
a thermoelectric material is also very advantageous due to the abundance of silicon as raw material and its ability to
be produced by regular IC manufacturing techniques leading to low cost. Here, our present works show a portable and
autonomous power generation microsystem based on a SiNWs μTEG coupled with an infrared plasmonic absorber for
heat-trapping purposes capable of powering micro/nano system.
One of the major sources of harvesting energy for the μTEGs is the human skin which is presented in our work. The
μTEG is integrated with a micro silicon-based plasmonic IR absorber plate in order to harvest thermal energy in the
IR regime. This enhanced μTEG/absorber hybrid exhibited an increased ability to trap minimum excess heat on its
surface owing to the IR absorber, resulting in a considerable enhancement in output power and conversion efficiency
when compared to a standard μTEG. In this work, full simulations of the absorber are performed in addition to
electrical and thermal simulations for the μTEG by using COMSOL Multiphysics Simulator. The integrated hybrid
microsystem is easily fabricated using standard CMOS processes and has many applications, such as the powering of
wireless sensors and the harvesting of lost heat from electronic components.

In this work, we present the design of a refractive Axicon lens to be used in refractive index optical sensing. The lens is designed to generate a Bessel – Gauss beam at the wavelength of 3.3 microns. At that wavelength, the absorption of the CH4 is maximum and thus a maximum change in the refractive index due to the CH4 gas is also expected. The intensity profile of the generated beam is quite sensitive to the index of refraction of the surrounding medium. Placing the optical detector at the point of maximum change in the intensity with refractive index allows the measurement of the refractive index change and hence the gas percentage with very high sensitivity. Our design shows sensitivity greater than 970 % per RIU. We also develop an analytical formulation for the intensity variation with the refractive index. The results obtained analytically are confirmed by the finite difference time domain FDTD calculation. From the analysis and the derived expressions, we demonstrate the effect of the Axicon base angle on the sensitivity and hence allow for the lens optimization to achieve maximum sensitivity for a target application.

An integrated refractive index gas sensor working in the Mid infrared (MIR) region and utilizing suspended silicon waveguide is presented. Although many integrated refractive index gas sensors have been proposed in the literatures, their operating wavelength is limited to the near infrared range. Our proposed gas sensors can operate in the mid infrared up to 10μm, were many gases have their absorption fingerprints in order to enhance the sensing performance. A finite difference solver is used to perform the sensitivity analysis of the suspended silicon waveguide in the MIR range for gaseous medium. The analysis shows that a suspended silicon waveguide can achieve high waveguide sensitivity with a minimal mode loss. Thus, we designed a high performance Mach Zehnder Interferometer (MZI) gas sensor using a suspended silicon waveguide as the sensing arm. Three dimensional finite difference time domain (3D-FDTD) solver is used in the design and optimization of two designs. One for the wavelength interrogation scheme of detection and another one for the intensity interrogation scheme. The first design, exhibits high wavelength sensitivity S=7028 nm/RIU and can reach high figure of merit (FOM) of around 180 RIU-1 for both wavelength and intensity interrogation methods with only 250μm sensing arm length. The second design furtherly enhances the intensity interrogation FOM to reach 370RIU-1 at the same length. Intensity interrogation needs only a laser source and a detector. Hence, using our sensor in intensity interrogation based read-out offers compact, low cost and mass scale fabrication which makes our proposed sensor a good platform for lab on chip technology.

In this work we study various types of photonic waveguides for gas sensing in mid-infrared (MIR) region. MIR region which contains the absorption peaks of many gases is the most suitable region for gas detection. Operating near the absorption peak of the gas to be detected enhance the sensor performance significantly as both real and imaginary parts of the detected gas refractive index are maximized, which enhance the sensitivity and leads to lower detection limit. Here we focus on refractive index sensors that relies on the detection of the real part (n) of the refractive index. Refractive index sensors are strong candidates for integrated on chip sensors, where a small sample volume is needed. One of the main parameters in designing refractive index sensor is waveguide sensitivity which is defined as the ratio of the waveguide effective index change to the medium refractive index change, Swg=Δneff/Δnmed. Thus rigorous sensitivity analysis using full-vectorial finite difference mode solver have been carried out to determine the waveguide sensitivity of such waveguides to gaseous medium. We use silicon on sapphire (SOS) platform to operate in the MIR region from 2μm to 6μm. For each structure we make sensitivity analysis once with undoped silicon and once with doped silicon to show how converting the same structure from dielectric to plasmonic will affect its performance as sensor. The dependence of the effective index, sensitivity and mode loss of each waveguide on the different waveguide dimensions was studied. Finally, a comparison between the proposed waveguides is provided.

We present the study and design of an optical switch based on a hybrid plasmonic-vanadium dioxide-based waveguide. The power-attenuating mechanism takes advantage of the phase change properties of vanadium dioxide that exhibits a change in the real and complex refractive indices upon switching from the dielectric phase to the metallic phase. The proposed switch was designed to operate under the telecommunication wavelength. The switch was analyzed by three-dimensional full electro-magnetic simulations. An ER per unit length of 4.32 dB / μm and IL per unit length of 0.88 dB / μm are realized for the proposed electro-optical switch. The proposed electro-optical switch has the advantages of small device foot-print, compatible with the existing VLSI-CMOS technology and broadband operation.

We propose various optical ring gas sensors. These gas sensors are promising candidates for integrated on-chip sensing. The sensing operation depends on the change in the effective index. We show a detailed study of different sensors utilizing the absorption wavelength of both methane and carbon dioxide gases. These sensors mainly operate at the range of mid-infrared wavelengths because it contains the vibrational resonance of the gases of interest. We provide the details about the dimensions and the material used in our different structures. Moreover, we report sensitivity up to 5938 nm / RIU, and the full-width-half maximum (FWHM) and figure of merit (FoM) for all designs are also calculated. We succeeded in squeezing the FWHM to 4.76 nm and increasing the FoM to 1744.72.

Mid-infrared (MIR) region is an important region for sensing applications because it contains vibrational resonance for many gases such as methane, carbon monoxide, carbon dioxide, sulfuric acid, ammonia, and acetone. Doped silicon with negative permittivity in MIR region can be used in plasmonic technology to design gas sensors which combining both benefits of silicon and plasmonic technology in MIR region. Fabricating plasmonic integrated devices became easier with current progress in Nanotechnology. Small foot print could be achieved by using Plasmonics technology. Additionally, silicon is CMOS compatible, tunable, and it has high mobility. In this paper we proposed a Fabry-Perot resonator made of doped silicon. Moreover, we studied the response of the Fabry-Perot resonator as a gas sensor in the presence of air, methane and carbon dioxide gases. Consequently, the sensitivity, quality factor and the figure of merit are calculated.

Hyperbolic metamaterial (HMM) has paved the way for sub-diffraction focusing inside the HMM due to the propagation of large momentum wave vectors in the HMM. However, these high momentum K modes exponentially decay outside the HMM which results in decaying of the focusing resolution in the near field of the HMM. In this work, we introduce both a HMM and a hypergrating structures for sub-wavelength focusing in air. Hypergrating is a structure that combines a HMM with a grating surface. The proposed structure consists of upper metallic slit integrated on HMM based multilayer of doped/intrinsic InAs with lower intrinsic InAs grating surface. HMM based multilayer of doped/intrinsic InAs has the advantage of tuning the focusing wavelength in the mid-IR range. The proposed structure has reported sub-wavelength focusing in air with value reaching 0.08 λ. Hypergrating structure shows focusing resolution enhancement of 0.08λ as compared to 0.15λ for a HMM without lower grating, both at wavelength of 7.3μm. The focusing resolution outside the hypergrating structure is much higher than that is observed in the HMM only due to the introduced lower grating. This structure demonstrates a good candidate for sub -wavelength IR imaging application in air.

In the realm of intensive research on metamaterials, particularly, the two-dimensional analogue, known as metasurfaces have attracted researchers due to their lower losses, high efficiencies and low cost as compared to plasmonic metasurfaces. Dielectric metasurfaces (DMs) have been widely reported to experience magnetic and electric dipole Mie type resonances, in which, upon tuning these two resonances, dielectric metasurfaces can exhibit spatially varying optical responses, phases and polarizations of scattered fields. Recently, dielectric metasurfaces have been used for color printing application with very high color vibrancy. However, the fundamental building blocks essential for the realization of optical metasurfaces are designed with uniform dimension nano structures, resonating at particular wave length, thus printing image only with particular color. In order to be able to cover the whole optical regime, the metasurface needs to be designed with tunable optical response to be able to print images with multiple colors. In this work, we report a cubic TiO2 metasurface which experience magnetic and electric dipole resonances in the optical regime. We are able to tune the reflection peak of both resonances using Nematic liquid crystal (LCs). LCs are anisotropic materials with controlled orientation based upon different applied voltages. Changing the orientation of the LC allows for tuning the resultant of the electric field component of the LC and thus the reflection peak of the metasurface can be tuned across the optical regime. We report a tunable DM for optical filters application using single dimension designed metausrfcae with efficiency close to 99 % covering three colors in the visible range: red, orange and green.

Electro-optical modulator is a key component in data-communication, telecommunication and optical interconnects. In this paper we propose a novel electro-optical modulator design that utilizes Michelson Interferometer based on the widespread Silicon-on-insulator (SOI) technology with 220nm thickness of the silicon device layer. The proposed modulator is working at the telecommunication wavelength 1550nm. Due to its high Pockels coefficient and CMOS compatibility electro-optical polymer (EOP) is used as an active material where its refractive index changes with the applied electric field. The Michelson Interferometer consist of directional couplers which are used in splitting and combining the input power to and from the interferometer arms with 50/50 ratio at 1550nm. Slot waveguide with EOP clad is used in the interferometer arms to achieve high optical field confinement in the EOP which maximizes the mode effective index change of the interferometer arms when applying voltage. Finite Difference Eigen mode (FDE) solver was used to calculate the mode field profiles, effective index and loss of the slot waveguide. By optimizing the waveguide dimensions, we have achieved a waveguide sensitivity Swg=dneff/dnEOP of 0.9135 at 1550nm. Three-dimensional finite-difference-time-domain (3D-FDTD) method was used in the analysis and optimization of our Michelson Interferometer electro-optical modulator. Results show that our Michelson Interferometer modulator exhibit lower VπLπ product than previously published SOI based modulators. Moreover, the modulator exhibit low insertion loss (IL) leading to high extinction ratio (ER) in addition to its CMOS compatibility. Thus, our proposed modulator allows for compact, high performance and low cost modulators.

Interferometers are one of the basic devices in many photonics applications. Interferometers can be used in the design of optical filters, wavelength de-multiplexing (WDM), electro-optical modulators and optical sensors. They can also form the building block of optical digital signal processor (DSP). In this work, we propose novel integrated Michelson interferometer based on the Silicon on Insulator (SOI) technology with 220nm silicon device layer and working in the near infrared region. The Interferometer consists of input splitter directional coupler, two waveguide arms and directional coupler combiner with loop reflector. The interferometer transfer function and its parameters including the free spectral range (FSR), the full width half maximum (FWHM) and sensitivity were derived analytically. Using our proposed interferometer instead of the conventional Mach Zehnder Interferometer (MZI) as optical filter, electro-optical modulator or sensor will reduce the size of the device needed by a factor of two while achieving the same performance. Here, we use our Michelson Interferometer with four different path length differences resulting in FSR from 0.8nm to 6.4nm. A strip waveguide with 500nm width platform is used. These devices are suitable for optical filtering as well as wavelength de-multiplexing WDM applications. The simulation results of the proposed designs are extracted using Lumerical MODE and INTERCONNECT software tools that use scattering matrices of optical components to determine the transfer function of photonic integrated circuits (PICs). The designs were verified with three-dimensional finite-difference-time-domain (3D-FDTD) solver and show good agreement. Finally, the designs were fabricated using Electron Beam Lithography (EBL) and characterized showing also good matching with the numerical simulations results.

Gas sensors have been widely used for different applications including chemical detection, quality assurance, environmental monitoring and medical diagnostics. Optical gas sensors exhibit higher sensitivity and wider dynamic range than their electrical counterparts. This work demonstrates a novel design for a gas sensor based on conventional Silicon-on-insulator (SOI) platform. The sensor design is based on interferometer working in the near-infrared (NIR) region where directional couplers were used in splitting and combining the input power to and from the two arms of the interferometer with 50/50 splitting ratio at 1550nm. Slot-waveguide is used in the sensing arm of the interferometer and strip-to-slot and slot-to-stip converters with high coupling efficiency were used for transforming the optical mode. Finite difference eigenmode (FDE) solver was used to calculate its mode field profiles, effective index, and loss to optimize the waveguide dimensions and to achieve a waveguide sensitivity of 0.7 at 1550nm for 220nm silicon thickness. Three-dimensional finite-dif-ference-time-domain (3D-FDTD) method was used in the analysis and optimization of the proposed gas sensor. Results show significant improvement in the figure-of-merit (FOM) and reduction of device area. The sensor also exhibits low insertion loss (IL) leading to a low detection limit. The proposed sensor is easily fabricated using CMOS technology which is essential for mass-scale fabrication, and thus a low-cost sensor can be integrated with optical fiber communication systems and optoelectronic systems. Therefore, the proposed sensor has the potential to be a key component in lab-on-a-chip (LOC) systems.

Using all-dielectric metasurfaces has be the interest of the scientific community recently. This is because the conventionally used plasmonic resonator-based metasurfaces have high ohmic losses in the optical domain. On the other hand, dielectric materials have minimal losses in the optical regime. Dielectric metasurfaces are based on dielectric resonators, periodic sub-wavelength structures that exhibit electric and magnetic resonance near the operation wavelength. In this work a novel all-dielectric metasurface design is studied using Electro-optic polymers. Applying an electric potential over the electro-optic polymer can change the steering angle of the metasurface. This study is done using finite difference time domain simulation for the optical behavior of this structure. This structure is CMOS compatible contrary to plasmonic metasurfaces.

We propose a fully CMOS compatible optical sensor based on the ring resonator mechanism. The waveguide structure of the sensor utilizes the silicon on insulator slot waveguide configuration. The analyte fills the slot and the cladding of the ring resonator. Since the optical power is enhanced and confined within the slot, then the overlap between the analyte and the optical power is maximized. The sensitivity of the sensor was measured to be 350 nm/RIU at the optical wavelength of 1.55 μm.

This work presents the study and the design of optical switch based on a hybrid plasmonic-vanadium dioxide based waveguide. The power-attenuating mechanism takes the advantage of the phase change properties of vanadium dioxide that exhibits a change in the real and complex refractive indices upon switching from the dielectric phase to the metallic phase. The proposed switch designed to operate under the telecommunication wavelength. The switch was analyzed by 3D full electro-magnetic simulations. An ER per unit length of 4.32 dB/μm and IL per unit length of 0.88 dB/μm are realized for the proposed electro-optical switch. The proposed electro-optical switch has the advantages of small device foot-print, compatible with the existing VLSI-CMOS technology and broadband operation.

Recently, semiconductor nanowires (SCNWs) have received much attention due to their crucial role in physiochemical science and their high prospect for essential applications in advanced devices such as solar cells, light-emitting-diodes, transistors and bio/chemical sensors. Vertically-aligned silicon nanowires (SiNWs) platform is considered as a strong candidate for advanced devices because of the high volume-to-surface area ratio as well as the high aspect ratio originating from the vertical structure. The CMOS compatibility of such a platform allows for cheap commercial manufacturing of nanophotonic integrated circuit. Nanowire diameter is usually on the order of several nanometers and is comparable to the Debye length and this often results in much larger sensitivity than their thin film. In this work, we design a vertically-aligned SiNW gas sensor optimized to detect carbon monoxide (CO) gas at the midinfrared (MIR) range. SiNWs of diameters of only 200 nanometers are grown on Si wafers. According to Liao et al, thin nanorods have a significantly better sensing performance than thick nanorods in the detection of C2H5OH and H2S (100 ppm) in air. In addition, (MIR) gas sensing is very useful and user friendly as the gases are directly detected when they flow through the active sensing region of the sensor with no required human interaction with the dangerous gases. Finite difference time domain (FDTD) simulations are performed to verify the results and a comparison between the FDTD results and the experimental ones are held.

In this work, silicon-based plasmonic nanoantennas was realized. Using silicon instead of metals as the material of choice in building such nanoantennas is advantageous as it enables the integration of nanoantennas-based structures into integrated-optoelectronics circuits built using the standard fabrication techniques in the electronic industry. It also allows for low cost mass production of the proposed devices. Upon light incidence on an array of nanoantennas, Localized Surface Plasmon Resonance (LSPR) is generated which causes an enhancement in the localized field inside the structure and in the near field zone. The enhanced localized field is manifested as an enhancement in the absorbed as well as the scattered field. Varying the surrounding material causes variations in the wavelength of the enhancement peak as well as the enhancement level itself. Hence, sensors can be built to facilitate sensing molecules with its characteristic vibrational transitions. In this paper, dipole and bowtie silicon nanoantennas are investigated. It is found that when using silicon with high excess carrier concentrations as the material of choice, the enhancement occur in the mid-IR spectral range which is red shifted compared to the enhancement produced when using metal such as gold or silver. Working in mid-IR is advantageous for sensing applications as the characteristic vibrational transitions of the majority of bio-chemical molecules happens in the mid-IR.

Using transparent conducting oxides, such as indium-tin-oxide (ITO), for optical modulation has attracted research interest because of their epsilon-near-zero (ENZ) characteristics at the telecom wavelengths. Utilizing ITO in multilayer structure modulators, optical absorption of the active ITO layer can be electrically modulated over a large spectrum range. Although they show advances over common silicon electro-optical modulators (EOMs), they suffer from high insertion losses (ILs). To reduce ILs and device footprints without sacrificing bandwidth and modulation strength, slot waveguides are promising options because of their high optical confinement. We present the study and design of an electro-optical absorption modulator based on an electrically tuning ITO carrier density inside an MOS structure. The device structure is based on the dielectric slot waveguide with an ITO plasmonic waveguide modulation section. By changing the dimensions, the effective refractive indices for the slot mode and the off-state mode of the plasmonic section can be matched. When applying electric field to the plasmonic section (on-state), carriers are generated at the ITO-dielectric interface that results in changing the layer where the electric field is confined from a transparent layer into a lossy layer. A finite difference time-domain method with perfect matching layer absorbing boundary conditions is taken up to simulate and analyze this design. An extinction ratio of 15.5 dB is achieved for a 10-μm-long modulation section, at the telecommunications wavelength (1.55 μm). This EOM has advantages of simple design, easy fabrication, compact size, compatibility with existing silicon photonics platforms, as well as broadband performance.

The surface-enhanced Raman scattering (SERS) active substrates with high enhancement factor are required to detect trace concentration of biological or organic molecules by using SERS techniques. This work presents the results of the detection of trace concentration of pyridine by using silver nanotrees (AgNTs) that were deposited on silicon. The different densities of AgNTs were fabricated by electroless deposition on silicon wafer by using aqueous solution of HF and AgNO3 with changing etching time. It was observed that with increasing the time of etching the density of the fabricated AgNTs increased at room temperature. The morphology of the fabricated AgNTs was studied by using field emission scanning electron microscope (FESEM). The AgNTs with high branching gave the highest Raman spectrum of pyridine. In addition, the optical properties of the fabricated AgNTs at various etching time have been investigated by using a UV-vis- NIR spectrophotometer. The absorption increased with increasing the etching time due to increasing of branches of silver on silicon substrate.

An optical modulator is considered one of the most fundamental components in an optical data communication system as it acts as a linking device between the optical and electrical parts of the system. Electro-absorption (i.e. electro-optical) modulation is one popular scheme in designing optical modulators; however, minimizing the device footprint in siliconbased platforms acted as a challenge. Few years ago, “plasmonics” field emerged as a good candidate that could possibly further reduce silicon-based modulators’ footprint. Unfortunately, existence of metals introduced huge propagation losses. Recently, transparent conducting oxides (e.g. indium tin oxide “ITO”) have been intensively used as active media in electro-optical (EO) modulators. They have a metal-like plasmonic behavior with extremely lower losses.

Under no biasing voltage, ITO acts almost as a dielectric. However, by carefully tuning the biasing voltage, the free carrier concentration beneath the ITO surface is changed. This allows a dramatic alteration in the complex permittivity of the ITO reaching an epsilon-near-zero (ENZ) value at some point. At this region, the ITO acts as a metal and a plasmonic mode is present at an ITO-dielectric interface. A heavily doped silicon slab can be used as a contact for the gating voltage to be applied on in order to accumulate free carriers on the ITO surface.

In this work, an all-silicon indium tin oxide-integrated electro-optical modulator is designed. The modulator exhibits superior parameters (e.g. insertion loss and extinction ratio) that outperform the current modulators based on the same technology.

Optical interconnects have been proposed to be the next generation interconnect solution to overcome the impending interconnect bottleneck. Large optical devices have hindered integration of electrical and optical components. Plasmonics have enabled nanophotonic components with sub-micron scale optical devices with similar size range as electronics and they promise to bridge the size gap between optical and electrical components. Surmounting research is suggesting that the electronics industry is starting to accept more variety materials in the fabrication process, the most important of which is graphene. The modulator is composed of a thin layer of silicon nitride – a few nm thick – sandwiched between two graphene sheets that are both electrically connected to the signal. Thin Al2O3 layers separate the graphene sheets from the ground electrodes on top and bottom. The electric field generated by applying a maximum of 5V on the graphene sheets changes the fermi level of graphene to switch between a highly lossy metal-like material and a dielectric material. Operating in the mid infrared regime, around 5 μm wavelength, when the Fermi level is located in the band gap, optical absorption is high. When the Fermi level is located away from the bandgap, absorption is minimized. Simulations show that the modulator exhibits over 7 dB / μm extinction ratio and less than 0.1 dB / μm propagation loss. By designing for 3 dB extinction ratio and less than 0.1 dB propagation loss, the footprint of the modulator is only 80 nm x 400 nm for feasible integration in future electronic chips without competing for space.

Using transparent conducting oxides (TCOs), like indium-tin-oxide (ITO), for optical modulation attracted research interest because of their epsilon-near-zero (ENZ) characteristics at telecom wavelengths. Utilizing indium-tin-oxide (ITO) in multilayer structure modulators, optical absorption of the active ITO layer can be electrically modulated over a large spectrum range. Although they show advances over common silicon electro-optical modulators (EOMs), they suffer from high insertion losses. To reduce insertion losses and device footprints without sacrificing bandwidth and modulation strength, slot waveguides are promising options because of their high optical confinement. In this paper, we present the study and the design of an electro-optical absorption modulator based on electrically tuning ITO carrier density inside a MOS structure. The device structure is based on dielectric slot waveguide with an ITO plasmonic waveguide modulation section. By changing the dimensions, the effective refractive indices for the slot mode and the off-sate mode of the plasmonic section can be matched. When applying electric field to the plasmonic section (on-state), carriers are generated at the ITO-dielectric interface that result in changing the layer where the electric field is confined from a transparent layer into a lossy layer. A finite difference time domain method with perfect matching layer (PML) absorbing boundary conditions is taken up to simulate and analyze this design. An extinction ratio of 2.3 dB is achieved for a 1-μm-short modulation section, at the telecommunications wavelength (1.55 μm). This EOM has advantages of simple design, easy fabrication, compact size, compatibility with existing silicon photonics platforms, as well as broadband performance.

In this paper, we demonstrate a plasmonic planar lens structure that can achieve subwavelength focusing of the infrared electromagnetic radiation. The lens is composed of metallic binary slits with different dielectric fillings. The index modulation approach of the filling materials is used to achieve phase modulation of the wavefront of the incident wave. Using this approach, we could achieve a phase range of 0.43π. The structure can focus the incident infrared wave in the subwavelength scale. The focal length attained is 44.69 μm and the achieved Full width at half maximum (FWHM) is 4.28 um for an incident infrared wave of wavelength 8 um. The transmission through the structure is 25.64 % at the design wavelength. The used metal is copper and the dielectric filling materials are silicon and air. Copper has lower losses in the infrared range than the traditional metals used in visible Plasmonics. Silicon has a higher melting point than the common dielectric materials used in refractive index modulation of the visible Plasmonic lenses. This temperature stability is a very important feature when working in the infrared domain. Besides being specifically suitable for the infrared range, copper and silicon are also CMOS compatible. Therefore, the proposed structure is suitable for integration in many potential infrared applications such as thermal imaging, medical diagnosis, thermal photovoltaic cells and heat harvesting. In addition, the fact that many molecules have unique absorption spectra or signature in the infrared range would facilitate the analysis and study of many materials and biological molecules using infrared miniaturized spectrometers.

Silicon photonics have been approved as one of the best platforms for dense integration of photonic integrated circuits (PICs) due to the high refractive index contrast among its materials. Silicon on insulator (SOI) is a widespread photonics technology, which support a variety of devices for lots of applications. As the photonics market is growing, the number of components in the PICs increases which increase the need for an automated physical verification (PV) process. This PV process will assure reliable fabrication of the PICs as it will check both the manufacturability and the reliability of the circuit. However, PV process is challenging in the case of PICs as it requires running an exhaustive electromagnetic (EM) simulations. Our group have recently proposed an empirical closed form models for the directional coupler and the waveguide bends based on the SOI technology. The models have shown a very good agreement with both finite element method (FEM) and finite difference time domain (FDTD) solvers. These models save the huge time of the 3D EM simulations and can be easily included in any electronic design automation (EDA) flow as the equations parameters can be easily extracted from the layout. In this paper we present experimental verification for our previously proposed models. SOI directional couplers with different dimensions have been fabricated using electron beam lithography and measured. The results from the measurements of the fabricate devices have been compared to the derived models and show a very good agreement. Also the matching can reach 100% by calibrating certain parameter in the model.

An optical modulator based on the racetrack resonator configuration is introduced. The structure of the resonator modulator is built from silicon nanowires on silica. The cladding and voids between the silicon nanowires are filled with an electro-optic polymer. The proposed modulator is fully CMOS compatible. When the resonance is tuned to the 1.55μm wavelength, it experiences a wavelength shift upon voltage application, which is measured at the output as a change in the power level.

In this paper, we propose an efficient approach to solve the BPM equation. By splitting the complex field into real and imaginary parts, the method is proved to be at least 30% faster than the conventional BPM. This method was tested on several optical components to test the accuracy.

High performance optical structures based on new platform for the design of photonic structures are proposed in this work. The platform is previously proposed and is based on the design of an ultra thin waveguide with narrow lateral thickness with low confined field inside the core waveguide which enables using this waveguide for building high performance photonic based sensors and modulators. An MZI based modulator is reported with extinction ratio of 20.36 dB. These values resulted in high performance photonic structures as compared to the conventional waveguide based structures delimiting some of the constraints when using photonic structures. Keywords: interference, modulation, sensing, photonic structures, Mach-Zehnder

This work studies the fundamental mode and dispersion relation of a slot waveguide made of intrinsic silicon as the high index region and Air as the low index region by solving the full vectorial wave equation using vectorial finite element method. The objective is to identify the effect of dynamically inducing high excess carrier concentrations in silicon on the slot mode and it dispersion. Tracking the slot mode over a range of wavelengths reveals a reduction in the slot mode effective index upon introducing high concentration of excess carriers. This can be exploited in the dynamic tuning of a silicon slot waveguide dispersion and hence the operation of any sensor based on such waveguide by dynamically generate excess carrier at runtime.

Currently, silicon nanoparticles (SiNPs) are of great interest due to their potential applications in various fields such like optoelectronics, microelectronics, photonics, photovoltaics, chemical, and biologic sensors. SiNPs Become the most important and well-known semiconductor because Si-based devices have dominated microelectronics for many decades. Indeed, the production of smart SiNPs materials to enhance absorption and light scattering is currently the most convenient approach.

Recently, plasmonic fractal-like structures have been determined to enhance photovoltaic device performances; indeed, through an efficient coupling of the incident light at different frequency bands into both the surface plasmon modes and the cavity modes, a broadband absorption enhancement can be accomplished.

Silicon nanoparticles exhibit fluorescence deriving from Si quantum dot structures which are produced during chemical etching, and it can be synthesized with unique optical reflectivity spectra. These unique characteristics allow porous silicon to exhibit a signal that is affected in a expected way when exposed to environmental changes, presenting possibilities for the development of advanced functional systems that incorporate sensors for therapeutic functions or diagnostic.

In order to prevent rapid degradation after administration and to increase their blood half life, biocompatible polymers coating was performed on silicon nanoparticles. Different type of biocompatible polymers (chitosan, polylactic acid, PMMA, or dextran,) can be used.

However, several methods have been developed for the synthesis of silicon nanoparticles such as chemical etching, sol-gel technique, laser ablation, sputtering process; hot-wire synthesis, ball milling process, and microemulsion.

The main objective of this research is to develop a new technique for coating or encapsulation of Nanoparticles to modify their surface properties by using different polymers. Furthermore, polymers are non-toxic, non-flammable, relatively inexpensive and recyclable.

To overcome the classic sensitivity vs selectivity trade-off often associated with sensors used in diagnostic applications, signature spectroscopic information that is characteristic of the molecules to be sensed can be exploited. Raman spectroscopy offers such information and is suitable for biological fluids. It is considered a label-free sensing method that inherently has excellent specificity. Sensitivity on the other hand is generally low unless amplification of the generally weak Raman signal is achieved. Surface enhanced Raman Scattering (SERS) employs localized surface plasmons on metallic nanoparticles to amplify this signal by several order of magnitude. In this work, SERS substrates were prepared by growing silver nanoparticles using electrodeposition on silicon nanowires that were prepared using metal assisted chemical etching. Experimental results agree with finite difference time domain (FDTD) simulation results. Using pyridine as a probe molecule, Raman signal intensity was found to correlate well with the pyridine concentration in the range 10-6 M to 10-9 M, indicating its applicability as a quantitative sensor. Very low concentration of pyridine, 10-11 M, was detected although at this low concentration the detection is only qualitative. The enhancement factor was calculated to reach 1011. Spot-to-spot, sample-to-sample, and batch-to-batch variation was studied to ensure repeatability, which had been a long-standing issue of low-cost SERS substrates. In addition, experiments over several days highlight the robustness of these SERS substrates. This work bolsters the use of SERS as a low cost sensing method with good sensitivity and specificity for a plethora of applications without compromising on repeatability or robustness.

A novel low power design for polymeric Electro-Optic reflection modulator is proposed based on the Extraordinary Reflection of light from multilayer structure consisting of a plasmonic metasurface with a periodic structure of sub wavelength circular apertures in a gold film above a thin layer of EO polymer and above another thin gold layer. The interference of the different reflected beams from different layer construct the modulated beam, The applied input driving voltage change the polymer refractive index which in turn determine whether the interference is constructive or destructive, so both phase and intensity modulation could be achieved. The resonant wavelength is tuned to the standard telecommunication wavelength 1.55μm, at this wavelength the reflection is minimum, while the absorption is maximum due to plasmonic resonance (PR) and the coupling between the incident light and the plasmonic metasurface.

The Mid Infrared MIR wavelength range offers many advantages in different applications. Chemical and biological detection are one of these applications, as it contains the absorption fingerprints of many gases and molecules. In addition integrated plasmonics are suitable platform for high sensitivity on chip sensors. In this paper we propose plasmonic Mach-Zehnder Interferometer (MZI) working as a gas sensor near the absorption fingerprints of many gases in the mid-infrared region. The proposed MZI contains a vertically stacked metal-insulator-metal (MIM) and metalinsulator (MI) waveguide. The sensitivity of MI waveguide is lower at higher wavelengths and also lower for gaseous medium than for liquid medium. In addition the losses of the MIM waveguide with oxide layer as insulator are much larger than the losses of the MI waveguide with gas as insulator which will result in poor visibility interferometers. Using a high index layer above the metal of the MI waveguide the sensitivity of the waveguide to gaseous in the mid infrared has been significantly enhanced. This layer also balances the intrinsic losses of both MI and MIM waveguides. The thickness and the refractive index of this layer have been optimized using finite difference modal analysis. Using this layer high sensitivity and high figure of merit (FOM) have been achieved for our MZI. This structure offers simple fabrication and low cost sensor that is suitable for rapid, portable and high throughput optical detection using multiplexed array sensing technique.

Energy conservation techniques have been widely explored in recent years for several applications: IR camouflage, solar absorbers and for IR thermal harvesting as well. While many absorbers have been demonstrated using plasmonic metal nanoparticles, surface texturing and low density broad band absorbers, they still encounter inevitable drawbacks. The state of art absorbers are either suffering instability over time or bulkiness which limit their practical application. Metamaterials have provided a significant improvement overcoming the aforementioned challenges through introducing ultra-broad band absorbers. However, the urge for CMOS compatible sub-wave length absorber that can be integrated for opto/electronic devices is still a major challenge. We demonstrate a mid IR silicon absorber using doped Silicon/Silicon Hyperbolic Metamaterial (HMM) integrated with sub-wave length Si grating. HMMs are characterized by their hyperboloid dispersion momentum space that provides large density of photonic states. By applying sub-wavelength grating on HMM, light from free space can be coupled to high propagation wave vectors of the hyperbolic modes upon breaking the momentum mismatch restriction, leading to noticeable absorption. We are able to show that an all Si based designed HMM is capable to achieve absorption across the mid IR wavelength range reaching absorption (A) of value 0.9.This proposed CMOS compatible Si-based absorber serves as good candidate for IR thermal harvesting application for on chips purposes.

Silicon nanowires (Si NWs) array have emerged as a promising route on the road to achieve highly efficient solar cells (SCs). The NWs SCs can achieve highly efficient light trapping with reduced cost and material usage. However, it is difficult to fabricate NWs with smoothed surfaces due to the deficiency in the fabrication process. The surface roughness of SCs is an essential parameter of the optoelectronic performance of these devices. In this paper, the effect of surface roughness on the optical and electrical performance of the NW SCs is reported and analyzed. The optical absorption and the generation rates are calculated using 3D finite difference time domain (FDTD) method while the electrical characteristics are calculated using finite element method via Lumerical device software package. In this investigation, short circuit current density, open circuit voltage and power conversion efficiency (PCE) are numerically studied to quantify the electrical performance of the reported structure. The simulation results show that the Si NWs with 10% surface roughness has higher PCE than smoothed Si NWs counterpart by 8.33%. This is due to the multiple scattering between the SiNWs which increases the light absorption and hence the PCE.

In this paper, a highly sensitive surface plasmon photonic crystal fiber (PCF) biosensor is reported and studied to monitor glucose concentration. The suggested design is based on a well-known large mode area (LMA) single mode PCF infiltrated by a plasmonic material. Additionally, an etching process is applied to increase the biosensor sensitivity. The numerical analysis is obtained using a full vectorial finite element method (FVFEM). The suggested biosensor based on a commercial PCF with plasmonic rod achieves sensitivity as high as 7900 nm/RIU with corresponding resolution of 1.26 × 10-5RIU-1. The analysis also reveals that the proposed biosensor has a linear performance which is needed practically. Therefore, the reported biosensor has advantages in terms of fabrication feasibility and high linear sensitivity

Metamaterials (MMs) are composite structures that exhibit non-conventional optical properties. Conventional threedimensional MMs are rather bulky, usually require complicated fabrication techniques and are not CMOS technology compatible. On the other hand, there has been a great ongoing interest in two-dimensional Metamaterials (Metasurfaces). Metasurfaces are two dimensional periodic structures that allow controllable change in the amplitude and phase of the incoming wave upon interaction that allows for designing ultrathin optical components with various functionalities. This can be achieved through optical resonances through the metasurface. These resonances can be achieved either through plasmonic antennae or dielectric resonators. Due to their lossy nature in the optical domain, plasmonic and metallic based metasurfaces can lead to inefficient operation and limit the applicability of such structures. In this work we discuss an all silicon metasurface design using cross-shaped unit cells. This cross design in addition to being polarization insensitive is capable of achieving phase difference from 0 to 2π by optimizing two degrees of freedom and thus offers a promising platform for various metasurface applications. We show through numerical simulations the properties of this polarization independent design and how it can be used for mid-infrared beam steering and lensing applications.

In this study, we report an easy and cheap fabrication technique of wide band omnidirectional antireflective black silicon surface based on porous and non-porous silicon nanowires (SINWs). This technique depends on one step silver electroless catalytic etching method (EMACE) in an aqueous solution of AgNO3 and HF. We found a commensurate relationship between the dimensions and the etching time. The fabrication technique was examined for large scale production potential. Wide band and angle near zero reflection is reported in the visible region due to the strong trapping and antireflection properties. Quantum size effect and phonon scattering is confirmed for the fabricated structure through Raman measurement. Black silicon based on porous and non-porous SINWs shows promising potential for photovoltaic, optoelectronic and energy storage applications.

Organic solar cells (OSC) offer a promising alternative to achieve highly efficient solar cells with low cost and easy fabrication. However, light absorption efficiency in OSC is limited due to the low carrier diffusion length and low exciton mobility. Plasmonic nanostructures have the ability to localize light in the organic active layer and thus increasing the light path length without increasing its physical thickness. Here, we exploited a new type of plasmonic nanostructures to achieve high and broadband absorption enhancement in organic solar cells. Zirconium Nitride (ZrN), as an example of refractory plasmonics, has one of the highest localized surface plasmon resonance quality factor. In this work, several new ZrN nanostructures such as spherical nanoshells and nanodisks are incorporated in organic solar cells. A theoretical analysis using finite difference time domain (FDTD) simulations is implemented to thoroughly analyze and compare these structures. Mie scattering and absorption efficiencies are calculated to analyze these spherical nanoshells in a polymer environment. A high and broadband absorption enhancement is achieved after their incorporation in the organic solar cell.

High reflection losses combined with low absorption capabilities and high velocity surface recombination are the main problems that deteriorate the efficiency of thin silicon solar cells. Therefore, Low cost and easy scalable fabrication of wide band, angle and self-cleaning antireflection coatings are of great importance for different optical applications especially solar cells. Random textured silicon nanocones are fabricated through electroless metal assisted chemical etching (EMACE) combined with ambient oxidation. Theoretical studies using Finite difference Time Domain (FDTD) simulation guided the experimental procedures in terms of dimensions and tolerance to reach the optimum dimensions and superior optical properties. The Optical numerical and experimental studies are revealed wide antireflection properties and strong trapping effects up to 60° through the entire visible wavelength. The textured structure modified the hydrophobicity of the solar cell into hydrophobic surface with self-cleaning properties.

Ion-exchange process is one of the most common techniques used in glass waveguide fabrication. This has many advantages, such as low cost, ease of implementation, and simple equipment requirements. The technology is based on the substitution of some of the host ions in the glass (typically Na+) with other ions that possess different characteristics in terms of size and polarizability. The newly diffused ions produce a region with a relatively higher refractive index in which the light could be guided. A critical issue arises when it comes to designing such waveguides, which is carefully and precisely determining the resultant index profile. This task has been proven to be hideous as the process is generally governed by a nonlinear diffusion model with no direct general analytical solution. Furthermore, numerical solutions become unreliable—in terms of stability and mean squared error—in some cases, especially the K+−Na+ ion-exchanged waveguide, which is the best candidate to produce waveguides with refractive index differences compatible with those of the commercially available optical fibers. Linearized finite-element method formulations were used to provide a reliable tool that could solve the nonlinear diffusion model of the ion-exchange in both one- and two-dimensional spaces. Additionally, the annealed channel waveguide case has been studied. In all cases, unprecedented stability and minimum mean squared error could be achieved.

An ultra-compact hybrid plasmonic waveguide ring electro-optical modulator is designed to be easily fabricated on silicon on insulator (SOI) substrates using standard silicon photonics technology. The proposed waveguide is based on a buried standard silicon waveguide of height 220 nm topped with polymer and metal. The key advantage of this novel design is that only the silicon layer of the waveguide is structured as a coupled ring resonator. Then, the device is covered with electro-optical polymer and metal in post processes with no need for lithography or accurate mask alignment techniques. The simple fabrication method imposes many design challenges to obtain a resonator of reasonable loaded quality factor and high extinction ratio. Here, the performance of the resonator is optimized in the telecom wavelength range around 1550 nm using 3D FDTD simulations. The design of the coupling junction between the access waveguide and the tightly bent ring is thoroughly studied. The extension of the metal over the coupling region is exploited to make the critical dimension of the design geometry at least 2.5 times larger than conventional plasmonic resonators and the design is thus more robust. In this paper, we demonstrate an electro-optical modulator that offers an insertion loss < 1 dB, a modulation depth of ~12 dB for an applied peak to peak voltage of only 2 V and energy consumption of ~1.74 fJ/bit. The performance is superior to previously reported hybrid plasmonic ring resonator based modulators while the design shows robustness and low fabrication cost.

Different electro-optical modulator designs based on electromagnetically induced transparency are proposed. A conductor–gap–silicon input waveguide is coupled to microrings-on-disks on each side. A low voltage modulating signal is applied to the modulator in a push-pull configuration, which changes the refractive index of the embedded layer of the electro-optical polymer. The proposed microrings-on-disks and cascaded microring modulators with submicron radii can efficiently modulate the light wave with moderate propagation losses. The microring-on-disk modulator achieved ultrasmall capacitance, 1.06 fF, and low power consumption, 2.12 fJ/bit. Both modulators have low insertion losses and high extinction ratios.

Engineering a low-cost graphene- based opto-electronic device is a challenging task to accomplish via a single-step fabrication process. Recently scientists have started focusing on the development and use of a laser-based method for efficient reduction of graphene oxide (GO) films at low-temperature. Our proposed technique utilizes a laser beam for non thermal reduction of solution processed GO layers onto film substrates. Compared to other reduction techniques, it is a single-step, facile, time consuming, non-contact operation, environment-friendly, patternable, low cost, and can be performed at room temperature in ambient atmosphere without affecting the integrity of either the physical properties or the lattice of graphene. Laser scribed reduced graphene (LSRG) is shown to be successfully produced and selectively patterned from the direct laser irradiation of graphite oxide films under ambient conditions. In addition, by varying the laser's intensity, power, and irradiation treatments, the electrical properties of LSRG can be accurately attune over five orders of magnitude of conductivity. Feature has proven difficulty with other methods. This credible, scalable approach is mask-free, does not require certain expensive chemical reduction agents, and can be performed at ambient conditions starting from aqueous graphene oxide flakes. The non thermal nature of this method combined with its scalability and simplicity, makes it very attractive for the manufacturing of future generation large-volume graphene-based opto/electronics.

The efficiencies of thin film amorphous silicon (a-Si) solar cells are restricted by the small thickness required for efficient carrier collection. This thickness limitations result in poor light absorption. In this work, broadband absorption enhancement is theoretically achieved in a-Si solar cells by using nanostructured back electrode along with surface texturing. The back electrode is formed of Au nanogratings and the surface texturing consists of Si nanocones. The results were then compared to random texturing surfaces. Three dimensional finite difference time domain (FDTD) simulations are used to design and optimize the structure. The Au nanogratings achieved absorption enhancement in the long wavelengths due to sunlight coupling to surface plasmon polaritons (SPP) modes. High absorption enhancement was achieved at short wavelengths due to the decreased reflection and enhanced scattering inside the a-Si absorbing layer. Optimizations have been performed to obtain the optimal geometrical parameters for both the nanogratings and the periodic texturing. In addition, an enhancement factor (i.e. absorbed power in nanostructured device/absorbed power in reference device) was calculated to evaluate the enhancement obtained due to the incorporation of each nanostructure.

Three dimensional optical simulations are performed to assess the design requirements for obtaining highly efficient tapered Si nanowires (TSiNWs)/polymer hybrid solar cells. To avoid the complex fabrication processes of Si p-n junctions, the TSiNWs are coated with a conductive polymer forming a large junction area between both materials and making the charge separation more efficient. The addition of PEDOT:PSS has been reported previously where the absorption occur in the Si only. P3HT:PCBM has been also used on top of Si nanostructures to enhance the absorption. However, the maximum absorption of P3HT and Si are in the same range resulting in competence between the absorption of each material. Thus, thick Si substrates are still needed to achieve decent absorption in these devices. We report a broadband absorption spanning the whole visible and near infra-red range of the solar spectrum with only 5 Microns TSiNWs coated with a low band gap polymer. The tapered structure provides efficient light trapping for the incident light enhancing the absorption in the short wavelengths. The addition of the low band gap polymer (pBBTDPP2:PCBM) significantly enhanced the absorption at long wavelengths (700-900nm). Thus, broadband absorption is attained without the need of thick Si substrates. Full 3D optical simulations were performed to optimize the polymer thickness and compare between the enhancements in absorption for different polymers.

One of the key issues limiting the efficiency of organic solar cells is the narrow absorption band of the polymer active layer. Thus, a huge amount of the incident sunlight is lost. Here, a new structure is theoretically proposed achieving wide band absorption in organic solar cells using multifunctional TiN nanowires. In addition to the plasmonic properties of TiN, it was reported that TiN has the capability to produce free carriers upon light absorption. Thus, the structure is based on the ability to collect these photo-generated carriers.

Using the combination of TiN and polymer significantly broadened the absorption band due to the ability of TiN to localize light inside P3HT:PC70BM in addition to its ability to absorb light at longer wavelengths. The optimized structure enhanced the absorbed power by 95% and the optimal short circuit current by 123% over the same structure without the TiN nanowires. Electric field distribution is studied at different wavelengths to gain further insight on the localization of light inside the structure.

In this work a detailed analysis of the scattering cross-section of silicon Nano-particles with high number of excess carriers in the near and Mid Infrared (MIR) is provided. The effect of different radii of the nanoparticles on the resonance peaks is studied using Mie theory and verified using FDTD. The effect of the level of excess carrier generated on the scattering cross section also analyzed. The study reveals many useful characteristics for such particles which behaves as plasmonic particles in the MIR. Using this study, different particles are designed as scatters in the MIR based on specific dimensions and excess carriers level. These particles can be utilized for infrared spectroscopy of different application such as gas and biomedical sensing in the MIR.

In this paper, a new solution for the wave equation using the BPM technique is proposed. The basic idea of this new technique is based on reformulating the BPM equation to separate the real and imaginary parts and utilizes real system matrices only for the propagation steps. The updated equation exploits leap-frog method to couple the real and imaginary parts of the field at each propagation step. A comparison between the proposed method of solution and the conventional one is made and show that the proposed technique in solving the BPM equation get an accurate results with more time efficient way. Our method is proved to be at least 30% faster than the conventional BPM in solving waveguide problems. Such method can open the door towards efficient computational algorithms for solving complex systems.

Due to its low cost and simplicity, ion exchange is considered one of the most commonly used processes to produce glass waveguides nowadays. This fabrication technology is based on the substitution of some ions already present in the glass with other ions having different sizes and polarizabilities. A careful study of the resultant refractive index profile is crucial in the impact on the waveguide characteristics. In this paper, we introduce, for the first time, a novel solution of the nonlinear diffusion equation that model this process using finite element method (FEM) approach. The ion exchange can be modelled as a nonlinear diffusion equation, as the exchanged ions Ka+ diffuse into their new sites where the original ions were existing. Numerical instabilities are encountered when solving for the exchanged ions with similar diffusion coefficients as in the case of Ka+/Na+, which is used in fabricating integrated optical devices with refractive index differences compatible with those of the optical fibers. Different novel FEM techniques are proposed in solving the problem in 1D space. The stability and accuracy of the different methods outperforms the current numerical methods and provide a good tool for highly nonlinear diffusion problem.

Plasmonic grating structures can be used in many applications such as nanolithography and optical trapping. In this paper, we used plasmonic grating as optical tweezers to trap and manipulate dielectric nano-particles. Different plasmonic grating structures with single, double, and triple slits have been investigated and analyzed. The three configurations are optimized and compared to find the best candidate to trap and manipulate nanoparticles. The three optimized structures results in capability to super focusing and beaming the light effectively beyond the diffraction limit. A high transverse gradient optical force is obtained using the triple slit configuration that managed to significantly enhance the field and its gradient. Therefore, it has been chosen as an efficient optical tweezers. This structure managed to trap sub10nm particles efficiently. The resultant 50KT potential well traps the nano particles stably. The proposed structure is used also to manipulate the nano-particles by simply changing the angle of the incident light. We managed to control the movement of nano particle over an area of (5μm x 5μm) precisely. The proposed structure has the advantage of trapping and manipulating the particles outside the structure (not inside the structure such as the most proposed optical tweezers). As a result, it can be used in many applications such as drug delivery and biomedical analysis.

Silicon photonics offer a promising solution to high speed chip-to-chip interconnects implied by the next generation of computing and communication systems. Electro-optical modulators are the key devices enabling data to be imparted onto an optical carrier wave to propagate in silicon photonic links. Modulators that utilize transparent conducting oxides as the electro-optical active layer in hybrid plasmonic waveguides have recently received a lot of attention. However, no study has considered embedding the conducting oxide in hybrid plasmonic ring and disk structures. In this paper, we propose a novel hybrid plasmonic micro-ring modulator employing an indium-tin-oxide (ITO) layer on silicon-on-insulator (SOI) platform. A pure standard silicon access waveguide is introduced and a detailed discussion of the coupling junction design is presented. Due to its unique electro-optical properties, a unity order change in the refractive index of ITO is attainable and exploited to make a significant shift in the resonance wavelength eliminating the need for high quality factor resonance without sacrificing power consumption. Unlike conventional ring modulators, the proposed modulation mechanism uses the combined effect of changes in both the real and the imaginary parts of the refractive index to control the resonance wavelength and extinction ratio. We comprehensively study the modulator performance and the transmission spectra using FDTD simulations. Optimization of the design leads to a high modulation depth of about 20 dB for an applied voltage of 2V. The design has an estimated total capacitance less than 2 fF.

In this paper, we propose a new design for Mach-Zehnder interferometer with different cross-sectional area than that for conventional silicon waveguide. The structure has a high sensitivity towards the surrounding media as compared to conventional silicon waveguides. This enabled using our design in different applications including optical sensing and modulation.

We introduce an ultra-compact plasmonic sensor for lab on chip applications. The device utilizes the heavily doped Si for introducing plasmonic effects. The use of heavily doped silicon instead of metals for plasmonic excitation has the advantage of reduced losses and CMOS compatibility. The proposed device has a simple structure, also it can be easily fabricated using the mature CMOS fabrication technology. The device structure is made of a heavily doped silicon layer, on a silicon dioxide substrate, while the silicon layer is etched to form a slot waveguide, and a rectangular cavity. The proposed plasmonic resonator is operational in the mid infrared spectral region. The sensor possesses a high sensitivity of 5000nm/RIU in the mid infrared range.

A fiber based plasmonic sensor design is proposed. In principle, both the top surface insulator/metal interface and bottom surface can support SPP decoupled modes. The combination of sensitive interferometric techniques and the optimization process of the design and the material yields to enhanced sensitivities in range of 11000 nm/RIU.

While optical interconnects is expected in the near future to provide the most definitive answer to the current bottleneck in further scale down of the electrical interconnects in VLSI circuits by replacing electrical interconnects altogether, it is currently hindered by the fact that traditional optical interconnect would usually require waveguides that are at least an order of magnitude larger than its electrical interconnect counterpart with a separation distance of few microns to avoid undesirable coupling. Plasmonics offer a solution to the waveguide dimension problem as the guiding mechanism in plasmonic waveguide depends on the coupling between electrons and photons and allow for using waveguides with sub-wavelength dimensions on the expense of greater losses. By using silicon with high concentration of excess carriers as the material of choice, we can acquire plasmonic mode in the near and mid infrared. In this paper we use slot waveguides with both intrinsic silicon with and without high excess carrier’s materials and investigate their transmission effectiveness over 90 degree bends. For silicon with high excess carrier concentration, the modes are plasmonic and allow for excellent performance in transmission through 90 degree bends. This enables dynamic control of routing over 90 degree bends by manipulating the number of free carriers through light excitation. The fact that the slot waveguide is used makes the optical interconnect has dimensions in the same order of magnitude as current electrical interconnects dimension.

Localized Surface Plasmon Resonance (LSPR) that occur in plasmonic nanoparticles due to interaction with electromagnetic waves at wavelengths larger than the nanoparticles themselves has been exploited in many application like solar cells, cancer treatment and spectroscopy due to the enhanced scattering and absorption cross sections that LSPR provides. Being able to control the resonance peaks of scattering in real time using light can be a valuable tool for sensing-related applications as well especially if it happens in the near and Mid-IR spectrum where most of the biological molecules can be sensed as such spectrum contains strong characteristic vibrational transitions of many important molecules . In this work presented here, we used silicon nanoparticles and increased the concentration of free excess carriers in the nanoparticles by light generation until the free carrier concentration was large enough to cause LSPR similar to what we get with nanoparticles made of Noble metals. The LSPR generated by Si nanoparticles with high concentration of free carriers caused the resonance peak to happen in near and mid IR. Depending on the level of carrier concentration which can be changed dynamically in real time, we can control the scattering resonance peak characteristics and position as shown in our work. Successful fabrication of the Silicon nanosphere is demonstrated as well.

Raman scattering is an excellent analysis tool because a wealth of information can be obtained using a single measurement. It can also be configured as a diagnostic tool as a label free sensing method. In that case, enhancing the Raman signal is important to improve the sensitivity and detect low concentrations of analytes. A nanoparticle showing a particular Raman enhancement shows a much higher enhancement when it is on a nanowire. This was also confirmed experimentally. We report on a simple fabrication method of silver nanoparticles and silicon nanowires decorated with these nanoparticles. The nanowires were fabricated using metal assisted chemical etching. The nanoparticles were formed using electrodeposition. Samples were then immersed in Pyridine. An enhancement factor of around 6 to 8×105 was observed for silver nanoparticles alone. By depositing the same nanoparticles on silicon nanowires, the enhancement factor jumped 10-fold to 7×106. Finite Difference Time Domain simulations showed that a range of enhancement factors is possible up to 109.

The objective of this work was to develop an integrated general purpose label-free optical sensor using standard photolithography on silicon-on-insulator platform for lab on chip applications. Shallow silicon waveguides have weak confinement in the silicon with lots of field in the cladding. This is advantageous in sensor applications due to the high light matter interaction. Here, we use our shallow strip waveguide platform to design a sensor employing a multimode interference (MMI) section. Utilizing a multi-mode section as short as 4 mm, the sensor exhibits sensitivity ranging from 417 nm / RIU to 427 nm / RIU with a figure of merit from 32 to 133.

We propose devices based on doped silicon. Doped silicon is designed to act as a plasmonic medium in the midinfrared (MIR) range. The surface plasmon frequency of the doped silicon can be tuned within the MIR range, which gives rise to useful properties in the material’s dispersion. We propose various plasmonic configurations that can be utilized for silicon on-chip applications in MIR. These devices have superior performance over conventional silicon devices and provide unique functionalities such as 90-sharp degree bends, T- and X-junction splitters, and stubs. These devices are CMOS-compatible and can be easily integrated with other electronic devices. In addition, the potential for biological and environmental sensing using doped silicon nanowires is demonstrated.

An intermediate reflector layer (IRL) serves as a spectrally selective layer between the top amorphous cell and bottom nanocrystalline cell in a micromorph silicon thin-film solar cell. In this paper, an IRL periodic design is proposed to achieve better conversion efficiency using thin active layers. The optically simulated short circuit current reaches 13.62 mA/cm2 and three-dimensional electrical analysis shows a promising result. The design methodology used in this paper can be easily applied to different types of IRL materials and extended to triple thin-films solar cells. Finally, the results are compared with state-of-the-art design and further enhancement factors are discussed.

We demonstrate an ultracompact integrated silicon-based plasmonic sensor for lab-on-chip applications in the mid-infrared (MIR) spectral range. Our sensor possesses desirable features such as design simplicity and very high sensitivity. The sensor is designed using a platform for plasmonic effects in the MIR using highly doped silicon. This platform is exploited to create a metal-less plasmonic slot waveguide in the MIR range. This plasmonic waveguide is highly sensitive to any environmental change. Full wave electromagnetic simulations were carried out to design and optimize the structure. The proposed sensor covers a large wavelength span in the MIR range. High spectral sensitivity of 5000 nm/RIU was achieved for our sensor device. Further development of the structure was conducted to extend the sensor operation to multigas sensing.

We propose a novel structure with two input and output silicon waveguide ports separated by the Insulator-Metal- Insulator channel deposited on silicon nitride base. In principle, both the top surface insulator/metal interface and bottom surface can support SPP a decoupled modes. Once the SPP modes excited input silicon waveguide, the SPP signals from the two optical branches (the top and bottom interfaces) propagate to the output silicon waveguide. At the output waveguide both branches interfere with each other and modulate the far-field scattering. The top surface is considered as the sensing arm of this plasmonic Mach-Zehnder interferometer (MZI). The bottom surface is considered as the reference arm of the sensor. High sensitivity and small foot print is achieved using this integrated simple plasmonic design. The combination of sensitive interferometric techniques and the optimization process of the design and the material yields to enhanced sensitivities up to 3000 nm/RIU.

An efficient sensitivity analysis approach for quantum nanostructures is proposed. The imaginary time propagation method (ITP) is utilized to solve the Time Dependent Schrödinger’s Equation (TDSE). Using this method, an extraction of all the modes and their sensitivity with respect to all the design parameters have been performed with minimal computational effort. The sensitivity analysis is performed using the Adjoint Variable Method (AVM) and results are comparable to those obtained using Central Finite Difference Method (CFD) applied directly on the response level.

Designing a miniaturized and efficient optical filter which can be actively tuned is a modern engineering challenge. This paper propose a design of a device with a nano scale size for active tuning the resonance frequency of a metal-insulator-metal plasmonics optical filter. The design is based on controlling the relative position between two stubs in metal-Insulator-metal plasmonics waveguide using NEMS technology. The mechanical design parameter is chosen carefully to be compatible with modern fabrication technology and a reasonable fabrication process of the device is proposed. The analysis of the mechanical and optical design is done and shows a promising performance. For the chosen mechanical design parameters, the optical resonance wavelength can be tuned from 1.45μm to 1.65μm using 7VDC actuation voltage.

We introduce a compact plasmonic resonator that is capable of generating a Fano resonance in the transmission spectrum. The Fano resonance is observed with its unique lineshape. The proposed design is simple, compact, easy to fabricate and can be easily developed for different applications. The device structure is made of a gold layer, a metalinsulator- metal waveguide, and a rectangular cavity. As an application to the proposed plasmonic resonator, we introduce a gas sensor which is operational at the near infrared spectral range. The sensor possesses a high sensitivity of 1500nm/RIU at the telecom wavelength 1.55μm. FDTD simulation tools were conducted for the optimization of the device structure and obtaining the results.

A highly selective plasmonic demultiplexer based on a plasmonic slot waveguide platform is proposed. The structure is optimized as an add drop multiplexer/demultiplexer. The optimal design is targeting minimum FWHM. The device is optimal quad multiplexer/demultiplexer has FWHM of 9.8 nm for each channel with a high output transmission near the 1550 nm. The proposed structure is simple, can be easily fabricated. Extended optimization was performed that enabled the multiplexed signal to have FWHM of 8.16 nm with peak power of 30 % near the 1300 nm. The structure can be utilized for double channel multiplexing applications and more by doing the needed optimization for such high scalability.

Thin film silicon based photovoltaic cells have the advantages of using low cost nontoxic abundant constituents and low thermal manufacturing budget. However, better long-term efficiencies need to be achieved overcoming its inherent bad electrical properties of amorphous and/or microcrystalline Silicon. For the goal of achieving best results, multijunction cells of amorphous and microcrystalline silicon thin layers are industrially and lab utilized in addition to using one or more light management techniques such as textured layers, periodic and plasmonic back reflectors, flattened reflective substrates and intermediate reflector layer (IRL) between multijunction cells. The latter, IRL, which is the focus of this paper, serves as spectrally selective layer between different cells of the multijunction silicon thin film solar cell. IRL, reflects to the top cell short wavelength while permitting and scattering longer ones to achieve the best possible short circuit current. In this study, a new optimized periodic design of Intermediate reflector layer in micromorph (two multijunction cells of Microcrystalline and Amorphous Silicon) thin film solar cells is proposed. The optically simulated short circuit current reaches record values for same thickness designs when using all-ZnO design and even better results is anticipated if Lacquer material is used in combination with ZnO. The design methodology used in the paper can be easily applied to different types of IRL materials and also extended to triple and the relatively newly proposed quadruple thin films solar cells.

We demonstrate absorption improvement in organic solar cells due to the incorporation of TiN nanopatterned back electrode. Organic solar cells (OSC) have already reached 10% power conversion efficiency (PCE), which made them comparable to commercial solar cells. Localizing light using plasmonic nanostructures has the potential to overcome OSC absorption limitations and thus further improve their PCE. Using a C-MOS compatible, cheap and abundant material for light trapping could facilitate the commercialization of OSC. This work theoretically shows that the replacement of Ag nanopatterned back electrode with TiN in plasmonic OSC gives enhanced performance. In addition, the incorporation of TiN nanoparticles inside the active layer has been studied and analyzed.

In this work we present novel and detailed dispersion the modal analysis of (SOS) strip waveguide in the mid-IR region. The effect of the various design parameters on each mode has been illustrated and carefully studied. The analysis has been extended to cover the fundamental and higher order TE and TM modes over the entire range of operation of this waveguides. The finite element method (FEM) and finite difference method have been both utilized to double verify the analysis. This dispersion analysis has been also utilized to propose novel functional devices in the MIR such as such as mode converter, switches, modulators and TE/TM-pass polarizer design based on the birefringence between the TE and TM mode.

In this work, we present an electro-optical modulator based on electromagnetically induced transparency (EIT). Our modulator employs a conductor-gap-silicon (CGS) microring resonator on each side of the input waveguide in a pushpull configuration utilizing an embedded electro-optical polymer (EOP). CGS waveguides support hybrid plasmonic modes offering a sound trade-off between mode confinement and propagation loss. The modulator is designed and analyzed using 3D finite difference time domain (FDTD) simulations. To have a high quality resonator, the rings are designed to have moderate waveguide propagation losses and a sub-micron radius of R = 805 nm. With an exact capacitance of just 1.06 fF per single microring resonator and applied voltage of 2 V, the exact energy consumption is estimated to be 4.24 fJ/bit. To the best of our knowledge, this figure represents 40% less power consumption in comparison with different modulators structures. The ultra-small capacitance of the proposed modulator and the instantaneous response of the used polymer make our design suitable for high bit rate applications. At the wavelength of -1550 nm-, the insertion loss is 0.34 dB and the extinction ratio is 10.23 dB.

Nanoelectromechanical systems (NEMS) design for active resonance frequency tuning of plasmonics optical filter is proposed and discussed. The design is based on controlling the relative position between two stubs in a metal–insulator–metal plasmonics waveguide using NEMS technology. The analysis of the optical design as well as the mechanical design is performed. Finally, a reasonable fabrication process of the device is proposed. For the suggested mechanical design parameters, the optical resonance wavelength can be tuned from 1.45 to 1.65 μm using 7VDC actuation voltage.

The mid-infrared (MIR) region is one of the most thriving spectral regions as it contains the vibrational resonances of several molecules of interest, as well as the absorption bands for hot bodies. In this work, we propose a novel dielectric waveguide that confines the light in a nanoscale air gap. This dielectric waveguide is a suitable candidate for on-chip sensing. Detailed dispersion analysis of this 3D waveguide is also provided. The effect of the refractive index change in the gap is studied and shows very high sensitivity and causes significant changes in the modal parameters. We also show that these waveguide modes exhibit plasmonic-like characteristics at the MIR region with controllable plasma frequency, without the inclusion of any metals. This waveguide is also utilized in various on-chip applications with nanoscale confinement at the MIR region.

Efficient, easy and accurate tuning techniques to a plasmonic nano-filter are investigated. The proposed filter supports both blue and red shift in the resonance wavelength. By varying the refractive index with a very small change (in the order of 10-3), the resonance wavelength can be controlled efficiently. Using Pockels material, an electrical tuning to the response of the filter is demonstrated. In addition, the behavior of the proposed filter can be controlled optically using Kerr material. A new approach of multi-stage electro-optic controlling is introduced. By cascading two stages and filling the first stage with pockels material and the second stage with kerr material, the output response of the second stage can be controlled by controlling the output response of the first stage electrically. Due to the sharp response of the proposed filter, 60nm shift in the resonance wavelength per 10 voltages is achieved. This nano-filter has compact size, low loss, sharp response and wide range of tunabilty which is highly demandable in many biological and sensing applications.

The vertically aligned Silicon nanowires are fabricated with optimized dimensions for energy applications. These nanowires are single crystalline with nanoscale diameter and micro scale length. These nanowires are fabricated in arrays for ultra wide band of absorption over all the visible domain. Unlike bulk silicon, the experimental measurements of these nanowires demonstrate maximum light absorption over ultra wide range of incident angles. Hence, these nanowires are considered as excellent candidate for cheap energy harvesting without antireflection coatings. Our experimental measurements have been also verified through electromagnetic simulations using finite difference time domain simulations.

In this paper, a novel meta surface is proposed for super-focusing. This surface contains two slits surrounded by finite corrugations for enhanced focusing. This simple surface has the super-focusing ability to focus both near and far field light in a hot-spot with FWHM much smaller than half the wavelength of the incident light. The structure is suitable for one dimensional and two dimensional focusing applications. The enhanced transmission through the double slit is also utilized for directional beaming over a wide cone of angles. Moreover, various structures have been proposed for superfocusing in the visible and ultraviolet wavelengths. The proposed structure lends itself to various applications including subwavelength imaging and nanolithography.

Optical biosensors present themselves as an attractive solution for integration with the ever-trending lab-on-a-chip
devices. This is due to their small size, CMOS compatibility, and invariance to electromagnetic interference. Despite
their many benefits, typical optical biosensors rely on evanescent field detection, where only a small portion of the light
interacts with the analyte. We propose to use a silicon nanowire ridge waveguide (SNRW) for optical biosensing. This
structure is comprised of an array of silicon nanowires, with the envelope of a ridge, on an insulator substrate. The
SNRW maximizes the overlap between the analyte and the incident light wave by introducing voids to the otherwise
bulk structure, and strengthens the contribution of the material under test to the overall modal effective index will greatly
augment the sensitivity. Additionally, the SNRW provides a fabrication convenience as it covers the entire substrate,
ensuring that the etching process would not damage the substrate. FDTD simulations were conducted and showed that
the percentage change in the effective index due to a 1% change in the surrounding environment was more than 170
times the amount of change perceived in an evanescent detection based bulk silicon ridge waveguide.

An analytical model to the modal characteristics of Metal-Insulator-Metal (MIM) plasmonic waveguide is
proposed. An expression to the propagation constant and losses as function in the refractive index, the
waveguide width, and the wavelength is obtained and verified using finite difference based mode-solver. These
expressions are used to develop a theoretical model to the behavior of a plasmonic nano-filter based MIM
configuration. The proposed model shows a good agreement with FDTD simulations. Using this model, the
sensitivity of the filter to different design parameters is investigated and analyzed analytically. Therefore, the
optimum values of different design parameters can be obtained analytically. By using this theoretical model, a
sharp resonance filter with narrow bandwidth, compact size, low loss, and good sensing characteristics can be
demonstrated. The proposed filter can be used in different applications such as, biological sensing and
communication systems.

An investigation has been performed of the low order guided modes in TiN 2D hollow metallic waveguide. The
dispersion characteristics of the TiN 2D hollow metallic waveguides key guided modes are identified and analyzed.
Dispersion manipulating is proposed by changing the material of the cladding region. The dispersion analysis of 2D
plasmonic waveguide using TiN has been investigated for the first time and compared to that of silver. A study has
been conducted on the effect of varying the material on the cutoff in the modes dispersion. The effect of changing
the plasmonic material on the dispersion curve key characteristics is also identified. Finally the effect of shifting the
cutoff on the enhanced transmission phenomena is investigated.

A simple analytical model is developed to estimate the power loss and time delay in photonic integrated circuits fabricated
using SOI standard wafers. This model is simple and can be utilized in physical verification of the circuit layout to verify
its feasibility for fabrication using certain foundry specifications. This model allows for providing new design rules for the
layout physical verification process in any electronic design automation (EDA) tool. The model is accurate and compared
with finite element based full wave electromagnetic EM solver. The model is closed form and circumvents the need to
utilize any EM solver for verification process. As such it dramatically reduces the time of verification process and allows
fast design rule check.

A theoretical analysis of plasmonic effects in a crystalline silicon-filled metallic nanohole is introduced. The dispersion properties of the guided modes of the silicon-filled silver nanohole are shown to have interesting characteristics such as negative dispersion, which is not normally observed in air-filled structures. Furthermore, the dispersion of the crystalline silicon material itself, when taken into consideration, significantly alters the dispersion characteristics of the guided modes. More interestingly, crystalline silicon is found to show metal-like properties at the edge of the UV/VIS spectrum; therefore, it is demonstrated that a silicon nanolayer surrounded by air is able to support surface plasmon polariton modes. The analysis is carried out using a full vectorial finite element method which can accurately detect the propagation properties of the structure under investigation.

Plasmonic materials, especially silver, are widely used to increase efficiency of solar cells due to their ability to localize the light in nanoscale. This tight confinement increases the absorption of a thin film solar cell. However, these materials are expensive and increase the cost/watt of the solar cell. Thus, finding an abundant and cheap material with a comparable plasmonic effect can dramatically reduce solar cell cost by enabling the use of ultrathin active layers. In this work, we investigate TiN as an alternative cheap and abundant plasmonic material. TiN is also more CMOS compatible. Several TiN plasmonic solar cell configurations are studied and analyzed. These studies show that the TiN plasmonic solar cell has a comparable performance for back side plasmonic configuration.

A sharp resonance, narrow bandwidth plasmonic cascaded nanofilter is proposed. The resonator is based on Metal-
Insulator-Metal (MIM) plasmonic waveguide which has the ability to confine light at sub-wavelength scale. The
proposed inline resonator features low loss, compact size, and good sensing characteristics which opens the door for
many nanophotonic applications. This structure can be used in many applications such as sensing, biomedical
diagnostics and on-chip optical interconnects. For example, it can be used as a highly effective integrated sensor with
sensitivity up to 3000 nm RIU-1.

A theoretical analysis of nanoscale metallic hole filled with a dielectric material is presented. The dispersion characteristics of the guided modes of a dielectric-filled metallic nanohole show interesting characteristics such as negative dispersion which is not normally observed in air-filled structures. Moreover, the material dispersion, taken fully into consideration, is shown to have a significant effect on the modal dispersion of guided modes, specially, at visible range of frequencies. The analysis is carried out using a full vectorial finite element method which can accurately detect the propagation properties of the structure under investigation.

Using plasmonic waveguide for interconnects application is very promising direction to achieve high density integration
a good size compatibility with electronic devices. Thus, proposing compact and efficient functional plasmonic devices is
or prime essential to achieve the required system functionalities. Power splitters are widely used as one of the important
component of the optical interconnects and integrated photonic and plasmonics devices. We propose a simple, ultra
compact and wideband balanced power divider. The advantage of this device is compactness and ability to split the
power over wideband with negligible imbalance. The device is based on plasmonic slot waveguide configuration and has
submicron total foot print. To achieve the proposed optimized design, a simple and novel analytical model is utilized for
modelling the behavior or any plasmonic structure using circuit model.

The importance of wavelength division demultiplexers (WDM) reside in its aggressive use in many areas of industry which are based on signal processing, especially in the fields of telecommunications, optical computing, integrated photonics circuits and sensing applications. Plasmonic wavelength division demultiplexers are essential component for on chip nanoscale plasmonic systems. In this work, we present nanoscale plasmonic wavelength-selective demultiplexer based on feedback resonator. The devices are based on a thin layer of silver with waveguides etched onto it having small foorprint. These devices can be easily tuned to any specific wavelength in the IR range.

Nanoplasmonic optical interconnects is proposed to mitigate challenges facing electronics integration. It provides fast
and miniaturized data channel that overcome the diffraction limit. We present a three dimensional plasmonic coupler that
vertically bends the light to multilevel circuit configurations. It exploits light guiding in nanoscale plasmonic slot
waveguides (PSWs). A triangularly-shaped plasmonic slot waveguide rotator is introduced to attain such coupling with
good efficiency over a wide bandwidth. Using this approach, light propagating in a horizontal direction is easily
converted and coupled to propagate in the vertical direction and vice versa. The proposed configuration is further
extended to the design of a multilayer power divider/combiner with ultra-compact footprint that guides the light to
multiple channels. A detailed study of the triangular rotator is demonstrated with the analysis of multiple configurations.
This structure is suitable for efficient coupling and splitting in multilevel nano circuit environment.

Plasmonic solar cell is a very promising structure for high efficient solar cell application. It has some unique
characteristics that allow high energy localization and higher solar energy absorption. Most of the proposed designs are
based on using noble metals such as gold and silver to achieve the plasmonic effect. These metals are, however,
expensive and increase the cost of the solar cell. Thus, the need to propose novel and cheap material with plasmonic like
effect is of prime importance. In this work we demonstrate the applications of TiN that has good plasmonic like effect
over wide bandwidth. A detailed comparative study of TiN and silver in an optimized design is presented, and we report
comparable TiN field localization and light scattering effects. In addition, TiN is more compatible with the CMOS
fabrication technology than the conventional plasmonic metals, which can even ease the integration with other
optoelectric devices. Should the electrical performance be further studied and optimized, the overall efficiency of the
solar cell can be maintained and/or enhanced and total cost/watt dramatically reduced.

We propose a novel sensing system using the plasmonic resonator for detecting a minor changes of the refractive index. The detection performance of our device has been numerically evaluated by (FDTD) finitedifference time-domain simulations. Our design can be easily fabricated using the focus ion beam milling technique. It leads to a highly compact sensor in terms with high sensitivity and high detection limit.

An integrated plasmonic resonator was proposed and analyzed. The detection performance of our device has been numerically verified by finite-difference time-domain simulations. The spectral sensitivity obtained was found to be 700 nm/RIU, where RIU is the refractive index unit. Our proposed sensor was found to have a detection limit in the order of 10−6 RIU. The plasmonic sensor could be fabricated using focus ion beam milling. Our design leads to an ultra-compact sensor suitable for on-chip sensing applications associated with a high sensitivity. For biosensing, the proposed sensor could have the ability for a specific capture of biomolecules at the sensor surface that enables for quantification of the biomolecules.

In this paper, we present our recent measurement of second harmonic generation (SHG) from silicon nanowires which are vertically aligned. The SHG shows a great enhancement due to the increase of the surface area which breaks the symmetry of silicon lattice and increase the surface SHG. A high SHG is also obtained in counter polarization for both S and P polarization excitation. An enhancement of 80 times is also observed. This huge enhancement opens the door for novel applications including frequency mixing and frequency generation for various novel nonlinear application of silicon based devices.

Metal-insulator-metal plasmonic waveguides (plasmonic slot waveguides, PSW) are known to offer high propagation lengths and confinement factors and have recently been gaining increasing attention in the literature. We analytically study the interplay between group velocity dispersion and self-phase modulation on ultrafast surface plasmon-polariton (SPP) pulse-reshaping for plasmonic-slot waveguides with nonlinear dielectric core. The analytic investigation of the role of the core nonlinearity on pulse propagation has, to our knowledge, not been investigated in the literature. We correlate our analytical results with numerical FDTD simulations.

We discuss a novel finite element method-based technique for estimating accurate sensitivities of the desired response. Our technique utilizes the central adjoint variable method (CAVM) for estimating the response sensitivities. This approach features accuracy comparable to that of the central finite difference (CFD) approximation at the response level. Our approach uses a simple perturbation method to calculate the sensitivity of modal parameters of various waveguide structures with respect to the geometric and material parameters. No additional simulation is required to calculate the response and its sensitivity with respect to all the design parameters. The accuracy of our approach is illustrated by comparing the results with the second order accurate CFD applied on the response level. Our results show a very good agreement between the CAVM-based sensitivities and those obtained using the expensive central.

In this paper a novel approach for optical beam splitting for MEMS based Fourier transform spectrometer is proposed. This approach is mainly based on spatial truncation of the input Gaussian beam into two symmetric Semi- Gaussian beams using V shape mirror and hence eliminating the use of a beam splitter and allowing the integration of optical spectrometers. It can be used over wide spectral range including infrared and visible region. Unlike the traditional Michelson interferometers which return half of the optical power to the source, the reflected power is negligible. This enables the use of multiple reflecting mirrors increasing the optical path difference by a factor of four. The analytical model describing the beams propagation and interference is derived using Fourier optics techniques and verified using Finite Difference time domain method. Mechanical model providing the mirror displacement to produce the optical pass difference is conducted and verified using finite element method. Mechanical displacement of 160 μm is achieved which is multiplied by a factor of four, resulting is a resolution of 9 nm at wavelength 1.55 μm. Finally, the effect of different design parameters on the interference pattern, interferogram and resolution are demonstrated.

Plasmonic slot waveguide (PSW) provides unique ability to confine the light in few nanometers only. It also allows for near perfect transmission through sharp bends. These features motivate utilizing the PSW in various on chip applications that require nanoscale manipulation of light. The main challenge of using these PSWs are the associated high losses that allow for propagation length of ~10 μm only. However, this constraint plays a minimal rule for circuits designed to have footprint in the order of few micrometers only. Thus, designing PSW with compact size and superior performance is of prime essential. Finite difference time domain (FDTD) is usually utilized for modeling of such networks. This technique is, however, inefficient as it requires very fine grid and carful manipulation of the boundary condition to avoid spurious reflections. In the paper, we present our recent equivalent circuit model that is capable of accurately modeling the various junctions including T and X shapes. This model is highly efficient and allows for obtaining a closed form expression of the response of any network of PSW with accuracy comparable to the FDTD results.

We propose a surface plasmon multilevel coupler based on the orthogonal junction coupling technique between silicon
nanowires and plasmonic slot waveguides (PSWs). It couples light of different polarizations from a silicon nanowire into multilevel plasmonic networks. Two orthogonal PSWs are employed to guide each polarization to its respective port. The proposed structure splits the polarizations and allows for simultaneous processing at different horizontal layers. Our
device overcomes inherent polarization limitation in plasmonic structures by providing multilevel optical signal processing. This ability of controlling polarization can be exploited to achieve 3-D multilevel plasmonic circuits and polarization controlled chip to chip channel. Our device is of a compact size and a wideband operation. The device
utilizes both quasi-TE and quasi-TM polarizations to allow for increased optical processing capability. The crosstalk is minimal between the two polarizations propagating in two different levels. We achieve -4.5 dB transmission efficiency at
a wavelength of 1.55 μm for the different polarizations in the respective ports. A transmission efficiency of -21 dB is
achieved in the subsidiary port. We analyze and simulate the structure using the FDTD method. The proposed device can
be utilized in integrated chips for optical signal processing and optical computations.

Extraordinary optical transmission through a subwavelength aperture was discovered more than a decade ago. A single subwavelength aperture surrounded by a finite array of grooves on a thin metallic film is a design used by many authors to show subwavelength focusing. In this paper, a modified version of this design is introduced that, to the best of our knowledge, gives best results of this design in terms of the peak power and the full width at half maximum FWHM in the near field as well as the far field of the lens. Numerical simulations using Finite-Difference Time-Domain (FDTD) method coupled with perfectly matched layer (PML) boundary conditions verify that the proposed metallic lens can give a near (far) field focal point 125 nm (1.39 μm) away from lens with FWHM of 245 (299) nm at incident wavelength of 760 (610) nm with power enhancement of at least 2 times over the unmodified design. The dependence of this resonant focusing ability with a certain geometrical parameter defining the modified structure is extensively analyzed in the visible range of spectrum. Such a focusing plasmonic device has potential practical applications like NSOM and FSOM due to the simplicity in its design and fabrication and due to superior results in near and far fields of the lens.

We introduce a memory efficient approach for the reduction of the required memory storage in time domain transmission line modeling (TLM)-based adjoint variable method (AVM). The proposed approach is based on manipulating the TLM scattering matrices to remove all redundant calculations. The required memory overhead for our approach is drastically reduced to only 10% of that of the original TLM-based AVM. This represents the ultimate memory reduction preserving the same accuracy of previously reported AVM approaches. Utilizing this approach, we can conduct AVM calculations for dielectric bulk structures 10 times larger. Our algorithm has been verified by comparison to the expensive finite difference approaches.

We propose a novel approach for efficient design of large number of coupled microcavities. This approach is based on formulating the design problem as an convex optimization problem. This formulation allows for fast, efficient solution of the desing problem. A filter design using 150 coupled microcavities has been achieved in less than one second of simulation using personal computer. The proposed technique require no initial desing to start the optimization process.

We propose a simple and accurate technique for the design optimization of coupled resonator optical waveguides
(CROWs). The technique is based on tapering the coupling coefficients at the CROWs stages to achieve arbitrary
realizable filter response. A perturbation theory is developed for the linearization of the design problem. The coupling
coefficients are expanded around a known mean coupling value. By dumping the higher order perturbation terms, we
ignore the effect of multiple reflections among the rings introduced by the small adjustment of the coupling coefficients.
This is a first order accurate approach as it takes into account only multiple reflections introduced by the zero order
terms. The design problem is then formulated as an optimization problem. The optimal filter design is achieved by
solving a constrained linear least square problem. This optimization problem can be solved efficiently to get the global
optimal design. Our technique is accurate and efficient compared to other nonlinear approaches. Our technique has been
verified using different proposed targeted filter responses utilizing third, fifth, and tenth order coupled ring resonators.
Highly selective tenth order filter with flat response is proposed. We compared our results to the existing techniques to
prove its accuracy.

The Characterization of the material optical properties with terahertz time domain spectroscopy is usually formulated
as an optimization problem with an objective function representing the deviation of the theoretical scattering parameters
from the measured ones. Both the magnitude and phase of the scattering parameters are utilized.
For samples of unknown thickness, false estimation of the thickness limits the accuracy of the results. We propose an
accurate optimization technique that predicts the actual thickness by solving only one optimization problem. Our
technique is also efficient compared to other techniques that solve N expensive optimization problems. Dispersive
dielectric models are embedded for accurate parameter extraction of a sample with unknown thickness.
For doped semiconductors we utilize the surface Plasmon Polariton behavior for accurately estimating the doping
level of semiconductor sample of unknown characteristics. By estimating the frequency at which the negative
permittivity exists, we can accurately estimate the doping level of the semiconductor. Our technique has been
demonstrated to be efficient and accurate through a number of examples.

We present the details and characteristics of graded index multimode mode interference (GIMMI) and its applications in optical communication components. This structure has unique features that allow for less sensitive wavelength dependant than the step Index case. This feature allows for wideband applications. In this paper, we present the applications of this structure to design wideband ultrafast integrated optical switch and integrated wideband polarization splitter. The graded index effect is produced using stair case index profile that mimics the parabolic index profile. The MMI with parabolic index profile has the analytical expression for the imaging length which provides simple design equations for the whole structure. The accuracy of this model is verified using 3D full vectorial beam propagation method.

In this paper, we discuss the recent achievements in realizing plasmonic networks, which are compatible
with silicon photonics platform. Obtaining good coupling between plasmonic gap and silicon waveguides is
necessary for these networks to be practical. We report our experimental realization of novel wide band,
and non-resonant coupling scheme between plasmonic gap and silicon waveguides.

Existing parameter extraction techniques in the terahertz range utilize the magnitude and phase of the transmission
function at different frequencies. The number of unknowns is larger than the number of available information creating a
nonuniqueness problem. The estimation of the material thickness thus suffers from inaccuracies.
We propose a novel optimization technique for the estimation of material refractive index in the terahertz frequency
range. The algorithm is applied for materials with arbitrary frequency dependence. Dispersive dielectric models are
embedded for accurate parameter extraction of a sample with unknown thickness. Instead of solving N expensive
nonlinear optimization problems with different possible material thickness, our technique obtains the optimal material
thickness by solving only one optimization problem. The solution of the utilized optimization problem is accelerated by
estimating both the first order derivatives (gradient) and second order derivatives (Hessian) of the objective function and
supplying them to the optimizer.
Our approach has been successfully illustrated through a number of examples with different dispersive models. The
examples include the characterization of carbon nanotubes. The technique has also been successfully applied to materials
characterized by the Cole-Cole, Debye, and Lorentz models.

We propose a novel design of integrated polarization splitter/combiner with ultra wide bandwidth. The proposed design
utilizes the electro-optic (Pockels) effect in GaAs for splitting the polarizations. It also exploits the self imaging
phenomenon in MMI couplers with a parabolic index distribution in the vertical direction to significantly increase the
bandwidth. A stair case index approximation of this index profile is utilized to facilitate the fabrication process. The
fabrication of this profile is feasible through the current technology using multiple etching. Our proposed design
maintains a variation of less than 0.5 dB in the power coupling over a bandwidth of 400 nm. We also propose a novel
approach for design optimization of the proposed structure. This approach is capable of extracting the propagation
constants and their gradient with respect to all the design parameters. This allows for using gradient-based optimization
The computational time of this optimization procedure is only a fraction of that for other recently proposed approaches.

Rectangular waveguide is a very promising structure for different applications. It has some unique characteristics that
allow for wide range of application including slow and fast light, metamaterial, low loss energy transmission, and
sensing. The resemblances and differences between this waveguide configuration and metal-insulator-metal (MIM) are
discussed in this paper. A Description of the guided modes and their operating band is also given. We also studied the
characteristics of the fundamental TM-like mode of this structure for the first time. Its potential application in sensing
and low loss energy transporting is also demonstrated. The effect of the design parameters on the performance of the
rectangular waveguide is illustrated for different application. Slow light and negative refraction effects using this
waveguide design using TE-like mode is also demonstrated. Different designs are proposed using this structure for these
different applications. Square shape design allow for polarization insensitive applications which is one of the unique
characteristics of the configuration.

We present recent novel approaches for engineering the dispersion characteristics of guided wave structures. These
approaches are highly efficient and depend mainly on the exploited numerical method for calculating the modal
parameters. Using these approaches, the modal parameters and their sensitivities with respect to all the design
parameters can be obtained efficiently. The computational cost is much less than that for estimating the sensitivities of
these parameters using finite difference scheme. The former approach requires many additional simulations proportional
to the number of design parameters. Our approaches, however, need no additional simulation for obtaining the
sensitivity information. They require the construction of an adjoint problem whose solution is readily available using the
original simulation.

We propose a novel design of optical router or switch based on the multimode interference phenomenon in waveguide
with parabolic index profile. A stair case index approximation of this index profile is utilized to facilitate the
fabrication process. The fabrication of this profile is feasible through the current technology using multiple etching. A
new design methodology is also proposed to ensure that the response of the stair case MMI (SCMMI) imitates the
response of the parabolic MMI. In this methodology, a two-stage optimization procedure is exploited to obtain the
optimal design. Gradient-based optimizers are utilized in these two stages exploiting the wide angle BPM. The required
response gradient is efficiently obtained using the adjoint variable method. The proposed design has the ability to rout
or switch any wavelength over a wide bandwidth.

We propose a novel approach for efficient sensitivity analysis and design optimization of surface plasmon polaritons
(SPPs) based waveguide structures. This approach has been utilized to analyze and propose novel designs of different
structures. It has been exploited to design a novel SPP waveguide using a metal loaded on silicon on insulator (SOI)
for subwavelength applications. In this design, the SOI material is utilized due to its wide application in electronic
circuits. It also allows for strong guiding and hence subwavelength light confinement. The utilized metal is gold (Au) at
a wavelength of 1.55 μm. The effect of the different design parameters of this structure on the propagation length of the
fundamental TM mode is efficiently studied using the proposed approach. The imaginary distance 3D ADI BPM is
utilized to calculate the propagation length. The sensitivity information is then estimated using the adjoint variable
method without any additional simulations. The same approach is utilized to propose an optimized design of new 1x3
SPP power splitter/combiner using metal on insulator. In this design the multimode interference phenomenon is utilized.
Our goal is to minimize the insertion loss for practical applications. The optimized design has a low insertion loss of 1.5
dB and compact size.

We discuss a novel technique for accurately estimating the sensitivities of any desired response based on the finite
difference Beam Propagation Method (BPM). Our technique utilizes the central adjoint variable method (CAVM) for
estimating the response sensitivities. Using only one simulation of the photonic structure, the response and its
sensitivities with respect to all the design parameters are obtained regardless of their number. This approach features
accuracy comparable to that of the central finite difference approximation applied at the response level. The
effectiveness of our approach is illustrated by using different response functions and different structures. Our approach
utilizes virtual perturbations of the system matrices. Central difference scheme is utilized to calculate the sensitivity of
these matrices with respect to the designable parameters. This sensitivity is then utilized to efficiently estimate the
sensitivity of the objective function. This technique has been applied first to the scalar 2D BPM. It is also extended to
calculate the sensitivities of 3D structures using full vectorial BPM. The proposed approach achieves a significant time
saving in calculating the response and its sensitivities. The accuracy of our approach is verified through comparison
with the expensive and accurate central finite difference applied directly at the response level. We also utilized the
calculated sensitivities in gradient-based optimization algorithms to maximize the power coupling in 3D optical fiber
coupler.

We discuss a novel FDTD-based technique for estimating accurate sensitivities of the desired response. Our technique utilizes the central adjoint variable method (CAVM) for estimating the response sensitivities. This approach features accuracy comparable to that of the central finite difference (CFD) approximation at the response level. Using only two simulations, of the original and the adjoint photonic structures, the sensitivities with respect to all the designable parameters are obtained regardless of their number. Our approach uses the same update equations of the conventional FDTD for the adjoint problem, which simplifies the implementation. A self-adjoint approach based on CAVM (SA-CAVM) is also proposed to extract the sensitivities of the power reflectivity. Using this self-adjoint approach, only the original simulations are needed to evaluate the objective function and its sensitivities as well. Our approach can also supply wideband sensitivities. The additional cost in this case is mainly that of performing the discrete Fourier transform (DFT) which is negligible compared to the FDTD simulation cost. Our SA-CAVM approach is also utilized to minimize the power reflectivity of deeply etched waveguide terminators, and double layer antireflection coatings on laser diode (LD) facets which can be used as an optical amplifier. The accuracy of our approaches is illustrated by comparing the results with the second order accurate CFD. Our results show a very good agreement between the CAVM-based sensitivities and those obtained using the expensive central finite difference approximation.

Multimode interference (MMI) couplers are important integrated optical components for the optical signal processing and routing. The realization of these components by ion exchange on glass substrates is particularly attractive for low cost integration. The design and analysis of MMI devices have generally been based on the self imaging principle in step-index waveguides, whereas waveguides fabricated by ion exchange on glass are practically graded-index due to the nature of the thermal diffusion of exchanged ions. In addition, the ion exchange process results in a guide with depth that depends on the mask opening (the guide width) which causes a high insertion loss at the interface between single mode and multimode sections of the MMI. To overcome these problems 3D simulation of the ion exchanged MMI structures is strongly required. In this work such 3D simulation is achieved on two levels. First the non-linear diffusion equation describing the ion exchange process is solved numerically using a finite-difference method with a modified algorithm to ensure solution stability for an extended range of nonlinearity. The resultant index distribution is used in a wide angle 3D BPM to simulate the optical field propagation in the structure. This allows accurate prediction of the structure performance under different fabrication and excitation conditions. Based on this simulation technique, 3 dB MMI splitter design with tapered access guides is optimized by both geometrical mask design and process parameter variations. The optimization shows that both the tapering and the use of annealing process can significantly improve the performance of the devices.

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Advanced PhotonicsJournal of Applied Remote SensingJournal of Astronomical Telescopes Instruments and SystemsJournal of Biomedical OpticsJournal of Electronic ImagingJournal of Medical ImagingJournal of Micro/Nanolithography, MEMS, and MOEMSJournal of NanophotonicsJournal of Photonics for EnergyNeurophotonicsOptical EngineeringSPIE Reviews